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AIRCRAFT DESIGN SUBSONIC JET TRANSPORT

Analyzed by: Jin Mok

Professor: Dr. R.H. Liebeck

Date: June 6, 2014

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Abstract

The purpose of this report is to design the results of a given specification and to

optimized parameter variation that leads to data collection through Matlab and Excel. The sizing

of the aircrafts and the drawing of the aircrafts are done through Solidworks. The requirements

such as center of gravity, tail sizing, fuel capacity, and wing layouts are made and located to

locations that meets the criteria. The detailed drawing specification allows the analysis through

calculations to verify the criteria’s that are required. The safety and comfort level of passengers

are one of the key factor for the design layout of the two aircrafts.

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TABLE OF CONTENTS

I. Summary of Airplane Design Study………………………….………4

II. Description of the Configuration…………………………….……….8

- Configuration Data….………………………………………………....………..9

III. Configuration Drawings…………………………………………………….…11

IV. Conclusion…………………………………………………….….....13

V. Matlab Flow Diagram………………………………………………...…...……14

LIST OF FIGURES

Figure 1: Plot of DOC vs AR for Single and Twin Aisle configuration…………..…….………4

Figure 2: DOC vs AR 3 Engine 150 PAX Single Aisle Configuration..…………..….....………5

Figure 3: Whitcomb Integral Supercritical Airfoil…………………………………...…………9

Figure 4: TR-51 Airfoil………………………………………………………………………..…9

Figure 5: NACA – 0009 Airfoil………………………………………………………………….9

LIST OF TABLES

Table 1: Design Parameter Specification…………………………………….…………………4

Table 2: Final Preliminary Design Specifications……………………………….……..………7

Table 3: Payload Range Graph……………….…………………………..……..………………8

Table 4: Fuel Volume..………………………………………..………………….…..…………10

Table 5: Interior Configuration …………………………..……………..…….…………….…11

Table 6: CG locations…………………………………………………………………………..11

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I. Summary of the Airplane Design Study

Design Specification:

Number of Passengers 150 220

Weight of Cargo 3000 lbs 3000 lbs

Range Requirement 3500 nautical-miles 3500 nautical-miles

FAR-Takeoff Field Length 7500 feet 7500 feet

Landing Approach Speed 135 knots 135 knots

Cruise Mach Number 0.8 0.8

Initial Cruise Altitude 35,000 feet 35,000 feet Table 1: Design Parameter Specification

Design Specification and Problem

The purpose of this study is to two subsonic aircrafts, one to transport 150 passengers and

the other to transport 220 passengers while fulfill requirement of 3500 nautical-miles. This

examines how and why certain parameters affect each other in relation to the final direct

operating costs, and to find the most cost efficient design. The specified requirements give

numerous methodology that enables countless design parameters, in order to obtain optimal

direct operating costs. The preliminary design of the two subsonic aircrafts sizing requirements

are optimized for the direct operating costs. With the collected data, these data are optimized

through numerical and graphical analysis that selects parameters to output favorable economic

value. These analyses are the basis of the rationale for the selection of the optimized aircraft

parameters and the preliminary design of the two aircrafts.

The Matlab code gives capability to vary parameters with relative values of direct operating cost.

The ranges of aspect ratios and

the sweepback angles are varied

with number of engines and

produce eight sets of data for

two aircrafts, type of airfoil,

number of aisles, and number of

engines.

These data, concurs that at

sweep angles 25-30 degrees and

at aspect ratio of 6-8 gives the

Figure 1: Plot of DOC vs AR for Single and Twin Aisle Configuration (Dotted Line: Twin Aisle, Solid Line: Single Aisle)

0.12

0.122

0.124

0.126

0.128

0.13

0.132

0.134

0.136

0.138

4.5 6.5 8.5 10.5

DO

C (

$/T

on

-mile

)

Aspect Ratio

DOC vs AR 150 PAX 2 Engine Supercritical Airfoil Single vs Twin Aisle Configuration 5

1015202530355101520253035

Figure1: Plot of DOC vs AR for Single and Twin Aisle Configuration (Dotted Line: Twin Aisle, Solid Line: Single Aisle)

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optimal direct operating costs. Thus, with sweepback angle of 30 and aspect ratio of 7 was

selected for 220 PAX design. For the other aircraft for 150 PAX design favored sweepback angle

of 25 degrees and aspect ratio of 7. These two parameters selected are varied with other

parameters to calculate the optimal design specs.

The 220 passengers with single aisle twin engine configuration generates optimal direct

operating costs, however, the difference in the direct operating costs between aisle configuration

is by 0.0068 ($/Ton-mile). The twin aisle configuration for 220 passengers are to be chosen even

with higher direct operating costs because of the growth sensitivity and comfort level to the

passengers. The advance technology that are used for airframe are composites or Al-Li

structures. As composites give significant reduce in weight, it is not commonly used for airline

flights which operates numerous short range flights per day. The management of composite

structures will increase DOC whereas the usage of the composite structures for day-to-day flight

will decrease DOC through weight reduction. However, the risks that arise from composite

structure are producing, repairing and managing the airframe have the highest risk factors not

only to DOC, but also in chance of accidents. It is because even composites have weight

reduction, processing the carbon composites are arduous and will produce increase in labor cost.

Composite structures cannot have air bubbles within the layers and detection of these bubbles

through ultrasonic is arduous. Also, reparation process of composites are not simple, new

0.127

0.129

0.131

0.133

0.135

0.137

0.139

0.141

4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5

DO

C (

$ /

To

n-m

ile )

Aspect Ratio

DOC vs AR for 150 PAX 3 Engine Single Aisle Conventional and Supercritical Airfoils 5

10152025303510152025303540

Figure2: DOC vs AR 3 Engine 150 PAX Single Aisle Configuration for both Airfoils (Solid Line: Supercritical Airfoil; Dotted Line: Conventional Airfoil)

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methods and more skilled inspection and inspectors needs to be trained. Contrarily, Al-Li alloy

structures yield weight reduction not as much as to composites, it has several advantages over

composites. During operation, the aluminum-lithium alloy structures can withstand stresses done

multiple daily flights. As well as damage control of this airframe has similarity to traditional

aluminum airframes where the damaged surfaced can be surface sanded for cracks and use scab

patches. Carbon composites contain higher strength with lower weight, however, in an impact

such as a crash, aluminum-lithium alloy absorbs energy as it is crushed, and the carbon

composites will shatter. In conclusion, even carbon composites composing strength of the

material and the weight reduction, aluminum-lithium alloys offsets carbon composites by robust

factors in production, maintenance, reparation process and the impact tests.

The usage of aluminum-lithium alloy in the airframe allowed reduction in direct operating cost

and weight. Carbon composite was not used even though composites yielded more weight

reduction, due to complex manufacturing, maintenance and repairs made aluminum-lithium alloy

appropriate material to be selected. As for 150 passenger aircraft are simply twin engine located

on wings, single aisle with Al-Li alloy which yielded the optimal direct operating costs. Two

engines are mounted on the wing to minimize the cost for both 150 and 220 passenger aircrafts.

The number of crew and stewardess were kept constant to have same comparison factors for

varying parameters.

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Specifications of the Preliminary Designs

PRELIMINARY DESIGN SPECIFICATIONS

Plane #1 Plane #2

Number of Passengers 150 220

WING PARAMETERS

Type of Airfoil Supercritical Supercritical

Sweepback Angle 25 30

Aspect Ratio 7 7

Span (ft) 101.12 120.64

Planform Area (ft^2) 1421.258 2079.04

Advanced Technology Used Used

FUSELAGE

Length (ft) 127.20 171.07

Diameter (ft) 13.08 14.66

ENGINE PARAMETERS

Type of Engine P&W - JT9D P&W - JT9D

Advanced Technology No No

Number of Engines 2 2

Location of Engines Wing Wing

INTERIOR CONFIGURATION

Number of Crew 2 2

Number of Stewardess 3 3

Number of Aisles 1 2

Number of Abreasts 6 7

WEIGHT

Structural Material Al-Li Alloy Al-Li Alloy

Take-Off Weight (lbs) 194001.10 276096.28

Fuel Weight (lbs) 64784.30 83258.54

Payload Weight (lbs) 35250 50300

OPERATION COSTS ( $ / TON-MILE)

Flight Crew 0.015323 0.011966

Fuel and Oil 0.051321 0.049864

Insurance 0.003063 0.002808

Maintenance 0.024357 0.021226

Depreciation 0.024182 0.022093

Direct Operating Costs: D.O.C. 0.118245579 0.10795736

Point by point inspection of the 150 and 220 PAX, it is concluded that both aircraft design would be

using two JT9D engines located on the supercritical wings. Wing span of both designs are critical due

to limits of hangar, limitations accustomed by FAR25 regulation, and the spans hold about 101 feet

and 121 feet for 150 and 220 passengers, respectively. Length of the fuselage heavily depends on

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interior configuration and the lengths generated are 127.20 feet and 171.07 feet, respectively. It is

rather costly to travel on smaller 150 PAX design than 220 PAX design because of 220 PAX design

yields lower costs even with twin aisle configuration. The effect of utilizing the wing parameters and

geometry from 220 passenger design to the 150 passengers. The sweep back angle is selected to be at

25 degrees for 150 passenger design configuration.

The payload range chart shows the distance that the specific aircraft can travel with payload and

the trade-off between the payload and the fuel to increase range. Point A-B has full payload with

2000lbs extra, point C is the design payload and range, point D is the trade-off between fuel and

payload, finally point E is full fuel with no payload.

A B C

D

E

0

10000

20000

30000

40000

0 1000 2000 3000 4000 5000 6000

Pay

load

in lb

s

Range (n-miles)

Payload vs Range 150 Passengers

A B CD

E

0

10000

20000

30000

40000

50000

60000

0 1000 2000 3000 4000 5000

Pay

load

in lb

s

Range (n-miles)

Payload vs Range 220 Passengers

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II. Description of the Configuration

Two aircrafts have been designed and 3D modeled based on the previous analysis. First

aircraft with 150 passengers and second aircraft with 220 passengers are met with the

requirements such as fuel capacity, center of gravity which leads to tail sizing, emergency exits,

lavatories, galleys, seat pitch, and aisle width diameter. The dihedral angle of the main wing and

the horizontal tail is to have lateral stability. Both aircrafts used Whitcomb Integral Supercritical

Airfoil as the main wing airfoils and TR-51 and NACA 0009 for horizontal and vertical tails,

respectively. First aircraft that are capable of carrying 150 passengers have dihedral angle of 7

degrees for both main wing and horizontal tail. Also, the second aircraft has 7 degrees dihedral

angle. The horizontal tails have different characteristics between both aircrafts. The first aircraft

has aspect ratio of 5 for horizontal tail and 1.5 for vertical tail, whereas the second aircraft had

the aspect ratio of 3.5. By having higher aspect ratio, the sweep angle was also 25 degrees for the

150 passenger aircraft, however, the area of the horizontal tail was much higher than that of 220

passenger aircraft. This can be an error caused in the calculations for tail sizing. The taper ratio

was same, however, the both aircraft used TR-51 airfoils. As for the vertical tail, the first aircraft

yielded aspect ratio of 1.5 and 1.2 for the second aircraft and used NACA-0009 airfoil for the

symmetric characteristic of this airfoil. The vertical tail on the first aircraft generated higher

surface area, but not as much as compared to horizontal tail. Every tail surfaces are swept back

equally as their main wing. Also, the volume coefficient for both aircrafts are held at 1.10 and

0.08, horizontal and vertical tail respectively. Both aircrafts also has same amount of doors and

emergency exit doors which are type A, 2 x B and I doors. The type B doors are mainly used for

entry and exits, and type A and I doors can be used as emergency exits. The number of lavatories

Figure3: Whitcomb Integral Supercritical Airfoil

Figure4: TR-51 Airfoil Figure5: NACA-0009 Airfoil

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and galleys were calculated to the function of how many passengers it holds to satisfy the

comfort level of the passengers and were located front and aft portion of the plane. To meet the

requirement of cargo and extra baggage of passengers, LD-W type containers are used for the

first plane and the LD-2/LD-3A type are used for the second plane. LD-2/LD-3A cargo

containers are bigger and holds more volume for the second plane and it was able to fit under the

cabin floor compartments. LD-W containers holds about 96.6 cubic feet and LD-2/LD-3A cargo

containers holds 266.55 cubic feet of volume. Total of 8 LD-W containers are used for first plane

and 5 LD-2/LD-3A containers are used for second plane. The location of these containers are

located front and aft portion of the wing so that it would not perpetuate the center of gravity. The

center of gravity is calculated for four cases: full fuel and full payload, full fuel and no payload,

no fuel and full payload, no fuel and no payload. The center of gravity was calculated and

determined to be at the position where these four conditions were within the range of 10%. The

location of center of gravity is critical due to tip-back and tip-over condition requirements that

need to be met. These requirements lead to tail clearance and landing gear sizing and its

locations. The landing gears and tires are chosen with the take-off weight. Determined by the

take-off weight, the first plane with 150 passengers, the main gear and nose gear dimensions are

given as: 46” x 14” (diameter x width), and 26” x 7.7”. Main gear has four wheels per strut and

the nose gear have two wheels. The second plane with 220 passengers needed larger tires due to

the take-off weight and its dimensions are: 46” x 16” main gear and 40” x 14” for the nose gear.

These landing gears have been accounted for the compression and static loading and with the

models shown, the lengths of the landing gears will fit into the fuselage. This chart shows the

fuel capacity of each aircraft.

The interior configuration of the both of the aircraft is different, while first plane for 150

passengers have more seat in the first class with 42” and 32” for economy, the second plane for

220 passengers have seat pitch of 40” first class and 34” for economy. The seat pitch for

economy is larger for 220 passenger aircraft because it uses 2-3-2 seats abreasts twin aisle

configuration. The number of lavatories, galleys and coat room are shown in the figure below.

Fuel Volume 150 PAX 220 PAX

Cubic Feet 1032.855 1566.24

US Gallons 7726.29 11716.3

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Interior Configuration 150 PAX 220 PAX

First Class Seats 12 20

Economy 138 200

First Class Seat Pitch (inches) 42 40

Economy Seat Pitch 32 34

First Class Seat Abreast 4 4

Economy Seat Abreast 6 7

Galleys 5 4

Lavatories 5 6

Rows 25 36

The detailed location of these interior items will be shown in the next pages with the interior

layout. The decision to locate the nacelle and the engine to be placed are determined to be near

the mean aerodynamic chord for both aircrafts, which uses two Pratt&Whitney Turbofan-JT9D

engines. The location of the engine was chosen to at near the mean aerodynamic chord, almost at

half the length of the wing. The next pages will give the summary and characteristics of the

aircrafts. The center of gravity is required to be within 10% of mean aerodynamic chord. This

chart provides the center of gravity for four cases that locates the main wing and satisfies the tip-

back and tip-over angles. The chart values are within the 10% range of the mean aerodynamic

chord

CG – 150 PAX Location Front Fuselage CG – 220 PAX Location Front Fuselage

Full Payload Full Fuel 40.1782 Full Payload Full Fuel 67.479

Full Payload No Fuel 45.9319 Full Payload No Fuel 65.3

No Payload Full Fuel 41.3902 No Payload Full Fuel 67.8

No Payload No Fuel 50.0243 No Payload No Fuel 65.113

Future References

The design of the two aircrafts for future consideration, the CG has to be calculated

carefully to satisfy the tail sizing conditions. It seems to have error in the tail sizing calculation

because of the values of 150 passenger aircraft tail surfaces are higher than that of 220 passenger

aircraft. The 3D modeling with Solidworks has been a challenge, however, the 3D modeling

made calculations and drawings much easier with huge time consumption.

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III. Configuration Drawings

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IV. Conclusion

In summary, the design specifications for both of the aircrafts are based upon the data

that were computed by Matlab and hand calculations and drawn by Solidworks. By

comparing two aircrafts side by side, the tail sizing have errors that were unforeseen. The

vertical tail for 220 passenger aircraft is too small and the surface area for horizontal tail for

150 passenger is too large. The interior configuration and other requirements are met such as

tip-over and tip-back requirements also the tail clearance angle for rotation. The number of

cargo containers, fuel capacity and the landing gear clearance requirements are satisfied with

the shown layout. Hence, the design specifications for the aircraft configurations are content

with surplus of minimum requirements.

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V. Matlab Flow Chart

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References

[1] J. Anderson, Aircraft Performance and Design, 1st . ed. University of Minnesota: McGraw-

Hill, 1993.

[2] R. S. Shevell, Fundamentals of Flight, 2nd, ed. Prentice Hall PTR, 1989

[3] B. W McCormick, Aerodynamics, Aeronautics, and Flight Mechanics, 2nd ed. Wiley, 1995

[4] J. Anderson, Introduction to Flight, 7th, ed. McGraw-Hill Science/Enginnering/math, 2011